Re: [PATCH master] resource: align memory reservation to page boundaries

[Sascha Hauer <sha@pengutronix.de>]

On Thu, Nov 09, 2023 at 12:30:12PM +0100, Ahmad Fatoum wrote:
> barebox remaps all reserved entries as uncached to avoid speculative
> access into the described regions using remap_range.
> 
> The ARM implementation requires buffers to be page aligned, which we
> can't assume unconditionally. For this reason, reserve_sdram_region
> will align region start and size before mapping uncached.
> 
> __mmu_init called later on, will remap everything outside the reserved
> entries cached, e.g. to cache additional DRAM not known at PBL time.
> No realignment will happen then though triggering the BUG(!IS_ALIGNED)
> in ARM's arch_remap_range.
> 
> By moving the realignment before __request_sdram_region(), we ensure
> that no misaligned memory regions will be passed to arch_remap_range by
> core code.
> 
> This fixes chainloading barebox from an older barebox[1] that reserves
> the FDT prior to relocation.
> 
> [1]: anything prior to 0b6b146a5508 ("fdt: Do not reserve device tree blob")
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  common/memory.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Applied, thanks

Sascha

> 
> diff --git a/common/memory.c b/common/memory.c
> index d560d444b0a8..300320f85344 100644
> --- a/common/memory.c
> +++ b/common/memory.c
> @@ -218,10 +218,6 @@ struct resource *reserve_sdram_region(const char *name, resource_size_t start,
>  {
>  	struct resource *res;
>  
> -	res = __request_sdram_region(name, IORESOURCE_BUSY, start, size);
> -	if (IS_ERR(res))
> -		return ERR_CAST(res);
> -
>  	if (!IS_ALIGNED(start, PAGE_SIZE)) {
>  		pr_err("%s: %s start is not page aligned\n", __func__, name);
>  		start = ALIGN_DOWN(start, PAGE_SIZE);
> @@ -232,6 +228,10 @@ struct resource *reserve_sdram_region(const char *name, resource_size_t start,
>  		size = ALIGN(size, PAGE_SIZE);
>  	}
>  
> +	res = __request_sdram_region(name, IORESOURCE_BUSY, start, size);
> +	if (IS_ERR(res))
> +		return ERR_CAST(res);
> +
>  	remap_range((void *)start, size, MAP_UNCACHED);
>  
>  	return res;
> -- 
> 2.39.2
> 
> 
> 

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